Ray Ingles asked:
“Why would substance dualism be an atheistic heresy? A minority position, to be sure, but you don’t need God for substance dualism. Nor faeries, for that matter.”
There really are two questions we might address in this regard. First, is adherence to substance dualism sufficient to make one an object of ridicule and censure within the atheistic community? Second, assuming the answer is yes, then why would substance dualism be sufficient to make one an object of ridicule and censure within the atheistic community?
Let’s consider the first question. Daniel Dennett, one of the leading new atheists, wrote the following in 1978:
“it is widely granted these days that dualism is not a serious view to contend with, but rather a cliff over which to push one’s opponents.”
This certainly sounds bad. According to Dennett, dualism is not a position that one can reasonably defend. Instead, it is a ridiculous position, which I take it is at least part of the reason for equating it with a “cliff”.
But note that in 1977, just the year before Dennett made this statement, the world famous philosopher of science Karl Popper and Sir John Eccles published The Self and its Brain, an erudite and powerful defense of substance dualism.
Substance dualism may have been a minority position among philosophers of mind back in 1978, but that hardly means it was ever a “cliff”. Consequently, I take Dennett’s comment to be not especially relevant to the philosophical promise of substance dualism within the philosophy of mind. Instead, it is revealing of the social censure with which atheists like Dennett want substance dualism to be viewed.
But why? As Ray observes, “you don’t need God for substance dualism”. This brings us to our second question.
Here we should distinguish between necessary incompatibility and natural incompatibility. (These are not great terms but they’ll do.) The distinction is straightforward. If two beliefs are necessarily incompatible then you cannot consistently hold them both simultaneously. If two beliefs are naturally incompatible then you can consistently hold them both simultaneously, but they are not a natural fit.
Let’s say, for example, that you are a member of the Republican Party and that you take a pro-choice view of abortion and are a strong advocate of gun control. It certainly is possible to be a Republican while being pro-choice and pro-gun control. But it certainly is not the most natural fit. And that would become obvious as you would express your opinions at various Republican meetings.
Similarly, substance dualism is consistent with atheism but is not the most natural fit with it. There are probably many reasons for this, but here are two:
(1) Substance dualism posits the existence of mental substances (i.e. minds/souls) that can intervene causally in the spatio-temporal material world. God is typically understood to be a mental substance that can intervene can intervene causally in the spatio-temporal material world. Given that many atheists believe the idea of a mental substance that can intervene causally in the spatio-temporal material world is incoherent or implausible, to accept the existence of such mental substances removes a significant objection to the truth of theism.
(2) It seems very implausible to think of mental substances coming to exist simply through evolutionary processes alone.
For these (and other) reasons, substance dualism is not a natural fit with atheism. And so it is hardly surprising that substance dualism as a position has been ridiculed by atheists as a cliff over which one pushes one’s opponent.